This invention relates generally to apparatus which utilizes vessels, valves and connecting conduits for the intermixing and/or diluting of fluids primarily for the purpose of making measurements and tests upon said fluid. More particularly, this invention is concerned with the type of automatic analysis instrument such as disclosed in U.S. Pat. Nos. 3,549,994 and 3,567,390 which employ the Coulter particle analyzing principle disclosed in U.S. Pat. No. 2,656,508. In particular, the invention herein provides improvements to the backwash system for diluting apparatus disclosed in U.S. Pat. No. 3,976,429 issued Aug. 24, 1976, owned by the assignee of this application.
In U.S. Pat. No. 3,976,429, a backwash system was provided, including a dispensing cylinder and valve arrangement for directing diluent as a backwash from a source to a sampling valve utilized to make dilutions and then to a sampler in a form of an aspirator tube introduced into a fluid, and a vessel was provided for catching the backwash fluid. Means were provided for aspirating the backwash fluid to waste. The vessel and the aspirator tube were positioned one relative to the other to enable the backwash to be received in the vessel only when diluent was dispensed as backwash. One of the aspirator tube and collector vessel was returned to its so-called normal condition relative the other either by movement of the tube relative to the collector vessel, or by movement of the collector vessel relative to the tube. Suitable controls were provided to assure that the backwash occurs only when the tube and vessel were in a relative relationship to receive the backwash.
One structure described in the last-mentioned patent comprises a receptor vessel in the form of hollow, segmentally configured vessel having an inlet opening in one wall thereof. The vessel was mounted pivotally for selective limited rotation about an axis taken through a corner thereof. Gears were provided to effect pivotal movement of the vessel about the mounting axis to align the inlet opening with the aspirator tube so that backwashed diluent could be delivered from the aspirator tube to the inlet opening. The backwashed diluent received in the collector vessel was removed therefrom by drawing a vacuum upon the vessel, the line leading to a waste container distant from the apparatus.
Some problems have been encountered during use of said backwash system. One problem involves the manipulation of the receptacle from an inactive to a backwash receiving condition. The inlet opening of the receptacle had to be placed into a disposition proximate to the delivery end of the aspirator tube but was spaced therefrom. Thus in the course of delivery, some splashing would occur. Not only was there a chance that some delivered fluid would be lost but the problem of contamination of the environment is present This is of particular disadvantage where the contents include contagions such as, for example, hepatitis causing organisms, possibly corrosive or chamically active fluids.
In the last mentioned patent, vacuum was only utilized to draw the backwash from the receptacle or collector vessel to a waste container. It also is important to provide means, as a part of the backwash system, to assure that the backwash be effected only when a sealed connection has been effected between the delivery end of the aspirator tube and the means provided to receive the backwash fluid and the residual material driven out thereby.